No abstract

Nerve growth factor (NGF) is a polypeptide that enhances survival, nerve fibre outgrowth and neurotransmitter biosynthesis in sympathetic and sensory neurones. Administration of antibodies against NGF to developing animals leads to atrophy of the sympathetic system. NGF is not normally detectable in innervated tissues but ablation of the innervating neurones leads to the production of measurable NGF in the target tissue. After transplantation of the denervated tissue, reinnervation occurs, then NGF decreases to undetectable levels. Thus NGF seems to act as a neurotrophic messenger and its level is regulated by innervating neurones. Because of the minute levels present it is very difficult to study NGF biosynthesis in innervated tissue. However, NGF can be isolated from male mouse submaxillary glands, where it exists in inexplicably high levels. Its amino acid sequence has been determined, and the synthesis of NGF and its larger precursors has been demonstrated in cultured submaxillary glands. We report here the nucleotide sequence of a submaxillary cDNA encoding the mouse NGF precursor (preproNGF). In contrast to previous suppositions the NGF moiety is situated near the carboxyterminus of the polyprotein precursor. It is flanked at the amino-terminus by 187 amino acids which may be cleaved at dibasic residues to generate three peptides; there are only two additional amino acids at the carboxy-terminus.

The structure of the messenger RNA (mRNA) encoding the precursor to mouse submaxillary epidermal growth factor (EGF) was determined from the sequence of a set of overlapping complementary DNA's (cDNA). The mRNA is unexpectedly large, about 4750 nucleotide bases, and predicts the sequence of preproEGF, a protein of 1217 amino acids (133,000 molecular weight). The EGF moiety (53 amino acids) is flanked by polypeptide segments of 976 and 188 amino acids at its amino and carboyxl termini, respectively. The amino terminal segment of the precursor contains seven peptides with sequences that are similar but not identical to EGF.

Most of the mRNA sequences coding for alpha and beta tubulin in embryonic chick brain have been determined by sequencing of cloned cDNA copies of these mRNA copies of these mRNAs. From a 1,682-base pair cDNA sequence we have deduced the entire protein sequence for beta tubulin. For alpha tubulin, all but about 38 N-terminal amino acids have been deduced from the cDNA sequence. Although tyrosine has previously been shown to be post-translationally added to the C-terminus of alpha tubulin by a specific ligase, we conclude that the primary post-translational even must be the removal, not the addition of tyrosine because a terminal tyrosine is encoded by the mRNA.

DNA extracted from hepatitis B virus Dane particles has been cloned in bacteria using a plasmid vector. A full-length clone has been examined by restriction endonuclease analysis, and the nucleotide sequence of an 892-base pair fragment from cloned hepatitis B viral DNA encoding the surface antigen gene is reported. The amino acid sequence deduced from the DNA indicates that the surface antigens is a protein consisting of 226 amino acids and with a molecular weight of 25,398. The portion of the gene coding for this protein apparently contains no intervening sequences.